According to Occupational Safety & Health Administration (OSHA), about 30 million people in the United States are exposed to hazardous occupational noise every year (Internet, United State Department of Labor, OSHA, Safety and Health Topics, 2014). Noise-related hearing loss has been listed as one of the most widespread occupational health concerns in the United States for more than 25 years. Thousands of workers every year suffer from preventable hearing loss due to high workplace noise levels. Rosenhall U, Pedersen K, Svanborg A (1990). “Presbycusis and noise-induced hearing loss”. Ear Hear 11 (4): 257-63; Schmid, R E (2007 Feb. 18). “Aging nation faces growing hearing loss”. CBS News. Retrieved 2007 Feb. 18; Senate Public Works Committee, Noise Pollution and Abatement Act of 1972, S. Rep. No. 1160, 92nd Cong. 2nd session.
According to Wikipedia; “Noise health effects are the health consequences of elevated sound levels. Elevated noise levels at workplace or other noise can cause hearing impairment, hypertension, ischemic heart disease, annoyance, and sleep disturbance. Changes in the immune system and birth defects have been attributed to noise exposure”. Passchier-Vermeer W, Passchier W F (2000). “Noise exposure and public health”. Environ. Health Perspect. 108 Suppl 1: 123-31.
Noise exposure also has been known to induce tinnitus, hypertension, vasoconstriction, and other cardiovascular adverse effects. Health Effects and Controls“. University of California, Berkeley. Archived from the original on 2007 Sep. 25. Increased levels of noise have been also found to be responsible for creating stress, increase workplace accident rates, and stimulate aggression and other anti-social behaviors.
A comprehensive report on effects of noise has been published in 1991 and it is a summary of the “Administrative Conference of the United States Noise and Its Effects” by Dr. Alice H. Suter, Conference Consultan, (November 1991).
A problem exists whereby there is a need to provide an ear attenuator which allows a user to change the amount of sound protection quickly and according to the amount of noise in the environment and also according to the need of being able to maintain communication. For example, at a construction site, at one moment the construction worker needs to be protected from very loud construction equipment and at a moment later the same construction worker may need to be able to recognize warning sounds or instructions given by a supervisor or may need to be able to recognize a warning sound from a piece of equipment.
In another example, a hunter needs to hear the faint sounds of the hunting animal but yet at the time of rifle fire he needs to protect his hearing. On a battle field soldiers need to protect their hearing from very loud explosions but also they need to hear commands as well as very faint sounds of their foes. In yet another example, a musician who wants to protect his hearing from the loud sounds of an orchestra may also need to hear instructions given by the conductor.
In a report from Stakeholder Meeting on Preventing Occupational Hearing Loss Washington, D.C. Nov. 3, 2011, Meeting Summary Report, quote “Hearing protection devices can interfere with speech and alarm detection for workers. This is especially true for many older workers, who already have noise-induced hearing loss. Hearing protectors often attenuate higher frequencies, which is the range in which speech and information is often conveyed. Making hearing protection devices compulsory puts some workers in danger. In fact, many workers find ways to sabotage hearing protection in order to communicate.”
One consequence of improper attenuation in hearing protection device (HPD) is that a user may reject the hearing protection (as cited above) if it compromises his/her hearing to the extent that sounds no longer appear natural, signals cannot be detected or localized, and/or speech is not intelligible. In some cases, too much attenuation may be provided by an HPD for a particular noise environment such that the user's hearing is unnecessarily compromised. The safety professional often faces a dilemma in selecting HPDs for the workforce. They are required to provide adequate attenuation for the excessive noise threat; at the same time they should provide safety for warning sounds allowing the worker to hear important signals and/or speech communications. The safety officer faces a dilemma of under protection versus overprotection.
A review of patent applications for ear protectors reveals patents going back to 1946. There are presently several hundred patents addressing the issue of protecting human ear from excessive noise.
Most of the ear protectors are simply devices which occlude the ear with foam or another pliable material. They do not allow for any variability of the attenuation level. They are referred to as “passive ear attenuators”. On the other hand, another category of HPDs are referred to as active. These are devices which are noise level dependent and vary the attenuation level with the incoming noise level.
The impetus for the development of variable HPDs were two reports; one by Casali, J. G. and Gerges, S., “Protection and enhancement of hearing in noise”, in Williges, R. C., Ed. Reviews of Human Factors and Ergonomics, Vol. 2. Human Factors and Ergonomics Society Santa Monica, Calif., 7, 195-240, (2006) (“Casali 2006”); and Suter, A. H., and the second one; “The effects of hearing protectors on speech communication and the perception of warning signals” (AMCMS Code 611102.74A0011), Aberdeen Proving Ground, Md.: U.S. Army Human Engineering Laboratory, 1-32. (1989) (“Suter 1989”).
The Variphone™ is one such example of an adjustable-valve design and is constructed from a custom-molded impression of the user's ear canal. The attenuation adjustment range of the device is approximately 20 dB to 25 dB below 500 Hz. At higher frequencies, the range of adjustment decreases, while the maximum attenuation attainable increases slightly. However, this device does not allow for a transparency of the incoming speech sounds or other warning sounds when needed. Also, separate filters need to be inserted to change the attenuation level.
The Sonomax SonoCustom™ is an example of a selectable-damper design. This device can be fitted with a variety of attenuation dampers that provide the opportunity for discretely variable attenuation in a single device, and each damper has distinct spectral attenuation values and NRR. Furthermore, the SonoCustom™ is not a functional/practical system where the user can quickly adjust the attenuation level as desired.
There is also a full custom-molded option of the acrylic Variphone™ brand earplug as well as the silicone V-SIL™, both of which incorporate a duct into which selectable “filters” are inserted for different attenuation values. Again, the practically of such device is questionable and in its least attenuation mode it still impairs user's detection of important sounds.
Another device is the dB Blocker™ from Custom Protect Ear. This product is a vented, custom-molded earplug that offers different cartridge filters that can be inserted into the vent. Each cartridge comprises a unique damper/filter which affords a specific attenuation spectrum, and the selection of cartridge is based upon an analysis of the wearer's noise exposure and other needs. The cartridge is intentionally not user-replaceable, so the dB Blocker™ is returned to the manufacturer should a cartridge need replacement or changing. This device, therefore, is preset and does not allow the user to select his/her own attenuation level
Yet another category are filter-based devices where the user can select different inserts with a constant attenuation. One example is an Etymotic Research E-15 or ER-20 with two inserts; one of 15 dB attenuation level and one with 20 dB.
One more device is a Combat Arms Double End Shooter's ear plugs for military which has the double end which let you choose constant attenuation for indoor range shooting by choosing one end of the ear plugs or use the other end of the plugs to get variable noise reduction for tactical ops, hunting applications, outdoor range work and other situations where situational awareness is important. Again, the Combat Arms ear plug does not allow the user to vary level of sound attenuation as desired.
In U.S. Pat. No. 8,550,206 to Keady et al. involves hearing protection devices capable of tunable acoustic attenuation; “The invention relates further to ear plugs comprising a fluid-containing balloon for occlusion of the ear canal, which are capable of being adjusted for example by modifying fluid composition and/or fluid pressure within the balloon to vary attenuation at different frequencies of the audible sound spectrum.” One objection to such a device is that it is difficult to confine the fluid reservoir and another disadvantage is that the fluid body itself can act as a fairly good conductor of sound and thereby defeats to some degree the purpose of the attenuation device. Another foreseeable problem is that the inflated pressure may alter in the ear canal cavity over time as the device will move with time due to balloon flexibility. This may result in fluctuating changes in the attenuation level.
Therefore, it is desirable to develop an ear attenuator that solves all issues of adequate protection and overprotection by allowing the user to have variable control of the attenuation level.
It is also desirable to develop an ear attenuator that overcomes the disadvantages of the prior art.